Exhaust dyno testing

Hobot · Jul 27, 2015

Exhuast X-overs - that are not merging converging extractor collectors - are know for 3 things, mellower deeper tone, felt improvement in off idle low rpm response d/t less back pressure out two exits and not hurting nor helping on cam hi rpm power. Hotest places on each header, at desired rpm most benefit, away from head after at least the first main bend is best place to tap each pipe but effect still worth while just tapping in where ever possible, like worst place - close to exht ports. X-over only needs to be 1/3 main pipe diameter.

acotrel · Jul 28, 2015

Have you tried altering the exhaust cam timing to compensate for the back pressure of a 2 into I pipe ? I use 12 degrees advance over standard with the 850 cam. (I've got a combat cam which I intend to advance 6 degrees).The torque is massive and as I raised the overall gearing, the bike accelerated faster. If you change the exhaust configuration without trying different cam timings, you are probably missing out. Many years ago there was a 12 year period when I raced once a month. I tried lots of different things, changing one thing at a time, race after race.

Fast Eddie · Jul 28, 2015

acotrel said:
Have you tried altering the exhaust cam timing to compensate for the back pressure of a 2 into I pipe ? I use 12 degrees advance over standard with the 850 cam. (I've got a combat cam which I intend to advance 6 degrees).The torque is massive and as I raised the overall gearing, the bike accelerated faster. If you change the exhaust configuration without trying different cam timings, you are probably missing out. Many years ago there was a 12 year period when I raced once a month. I tried lots of different things, changing one thing at a time, race after race.

I'm quite new to Norton's Al, so forgive my ignorance here...

But try as I might, I have been unable to find a way of advancing the exhaust cam timing without seeing a similar change in the inlet timing.

Fast Eddie · Jul 28, 2015

Chris said:
Hi Eddie

Did you have a run on the road with all the discs removed & the blank end plate fitted? Steve said it would be road level noise & not loose as much power as you think.

Chris

Sorry Chris, I missed this question:

No I didn't experiment with the Supertrap style end can or discs. When I had a quick look at it, it didn't seem to fit (different diameter), and I didn't look very much more closely at it after this I'm afraid!

NRP make a bigger end can on their Maney style system that Nigel claims has been developed to maximise efficiency. At the moment, my intention is to go with the NRP system and have Nigel make two cans, one a Maney copy, and another giving under 105 db (for track events etc).

He is a busy guys though...

jseng1 · Jul 28, 2015

lcrken said:
We did manage to pass the AMA sound test a couple of times with the ex-Jim Schmidt monoshock Norton with this conventional reverse cone mega system, but I think we had a Norton-friendly guy running the test.

Ken

Those pipes were LOUD. I remember using rolled up hardware cloth to help pass the sound tests. Regs were not as tight back then and no one noticed if I removed the hardware cloth for the race.

Here's a silencer tip for everyone:

Use 1/4" hardware cloth and heavy fiberglass woven roving. Lay out the hardware cloth. Place a layer of heavy weave fiberglass woven roving down on 1/2 of the hardware cloth, fold over the hardware cloth so both sides of the fiberglass are covered. Roll it over some pipe to give it a tube shape so it overlaps a little. Shove it into your megaphone or muffler so the folded over end of the hardware cloth faces the exit (to keep the fiberglass from blowing out). Run a long 8-32 screw through the hardware cloth near the exit of the muffler to hold everything in place. Loctite the 8-32 nut. Shoot for a foot of length or more for effective silencing. I've used this setup for over 20 years in simple cylindrical mufflers with the exits cut off so its 2-1/2 diameter from the header to the end.

This is a simple, cheap, effective and reliable silencer. The woven roving is about 1/4" crosshatch and will not disintegrate and blow out like puffy or fine weave fiberglass. Make the ID of the hardware cloth tube larger in diameter than your header pipes for free breathing. If the woven roving ever blows out its easy to disassemble and replace.

Fast Eddie · Aug 16, 2015

Well, sometimes, things just don't go your way do they?

I got back from holidays just in time for Beezumph, but, looking at a very busy few months ahead, and keen to progress with the exhaust Dyno testing, I decided not to go and enjoy myself at Cadwell, but spend the day on the Dyno instead (sad or what)!

So imagine my disappointment when, I find out on the day that my Dyno man has resigned!!

So, instead, I spent the day making brackets, moving the battery to allow the side panel to be moved I wards, etc, in order to properly mount the borrowed Maney system (thanks again Chris).

I think it looks ace! But its bloody noisy, and not a particularly nice noise either.

So, sir Comstock will be working his magic on my currently stock RH10 head this winter, I shall then re-run the bike on the Dyno. Then I'll be able to see which exhaust set up is best. The Maney will have to be very good in order to out weigh the appeal of the looks and sound of twin peashooters to be honest!

It will be very interesting to see what the effect of a good cylinder head job has on performance and power delivery characteristics (and to those who I have discussed the relative merits of cylinder heads with, yes, yes, I know. I did want a FA head. I really did. But given the lack of data of their effect on performance, I just couldn't justify the extra cost).

Here's some pics of the bike with Maney system etc:

Chris · Aug 16, 2015

Hi Nigel

Lovely job on the pipes

You still have the spacer to mount the supertrap plates & the road end plate. I guess you want to try it as it is.
The pipe passes noise testing a 105db plus or minus the allowance. I no longer run it as I cant see the point of being excluded if It failed.

A link to hear the beautiful noise

[video]

[/video]

Chris

Fast Eddie · Aug 16, 2015

Chris said:
Hi Nigel

Lovely job on the pipes
You still have the spacer to mount the supertrap plates & the road end plate. I guess you want to try it as it is.
The pipe passes noise testing a 105db plus or minus the allowance. I no longer run it as I cant see the point of being excluded if It failed.

A link to hear the beautiful noise

[video]

[/video]

Chris

I'll have another look at the supertrap end Chris. I'll also have a look if it just needs re-packing.

Hope you weren't attached to the rust on the pipe matey, as I've given it a coat of paint fo' thee !

74ok · Aug 16, 2015

how much these dyno runs cost?

Fast Eddie · Aug 16, 2015

84ok said:
how much these dyno runs cost?

I was on the Dyno for half a day last time and it cost me £125.

74ok · Aug 16, 2015

tx, is there such a thing as a 1 shot run? or perhaps an hr?

jseng1 · Aug 16, 2015

Fast Eddie said:
84ok said:

how much these dyno runs cost?

Click to expand...

I was on the Dyno for half a day last time and it cost me £125.

There is some interest right now that the longer JS rods (with lightweight pistons) and longer dwell time at TDC means that the combustion is more efficient and so requires less ignition advance. Changing the timing both ways should bracket the preferred timing range. This is best determined on a Dyno. Let us know if you learned anything and be very careful to avoid any full power detonation for any length of time because that will result in the piston skirt forcefully slamming cockeyed in the bore leading to destruction if continued. Note that your higher compression with the taller piston and correspondingly smaller combustion chamber generally means less advance. Then again you mentioned that your timing slipped and you lost HP. So data collecting and sharing is welcome.

Fast Eddie · Aug 16, 2015

jseng1 said:
Fast Eddie said:

84ok said:

how much these dyno runs cost?

Click to expand...

I was on the Dyno for half a day last time and it cost me £125.

Click to expand...

There is some interest right now that the longer JS rods (with lightweight pistons) and longer dwell time at TDC means that the combustion is more efficient and so requires less ignition advance. Changing the timing both ways should bracket the preferred timing range. This is best determined on a Dyno. Let us know if you learned anything and be very careful to avoid any full power detonation for any length of time because that will result in the piston skirt forcefully slamming cockeyed in the bore leading to destruction if continued. Note that your higher compression with the taller piston and correspondingly smaller combustion chamber generally means less advance. Then again you mentioned that your timing slipped and you lost HP. So data collecting and sharing is welcome.

I agree with the theory Jim. Getting the squish band working, and the increased dwell time, should all lead to reduced requirement for ign advance. I haven't had chance to experiment with that yet. But will when I return with the re-worked head.